Clarify the introduction to color to make it clear both plcol0 and plcol1 set the current color which is used for all subsequent plotting actions.
Clarify the introduction to color to make it clear both
plcol0 and plcol1 set the current color which is used for all
subsequent plotting actions.

svn path=/trunk/; revision=12137

FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot,FreeScienceCommunity/PLPlot